Local officials and river aficionados celebrate the opening of a 2 1/2-mile stretch of the waterway — the first time it had been open to public navigation in decades.

Steve Schleier has kayaked spectacular and scenic rivers from West Virginia to Alaska. So when the Los Angeles lawyer heard that his hometown river was opening to public navigation for the first time in decades, he was all in.

It didn't matter that the open section is a mere 21/2 miles long. It didn't matter that the riverbed is lined with concrete. And it didn't matter that the course features more warehouses than white water.

For Schleier, like many Angelenos, the opening of a modest stretch of the Los Angeles River on Monday was about redemption and possibility.

"Today," he said, preparing to put in at Rattlesnake Park, where Fletcher Drive crosses over the water, "is like getting your toe in the water for the revitalization of the river."

Earlier in the day, local officials and river aficionados gathered to celebrate the opening of the section between Fletcher and Oros Street as a recreation zone for the summer. The designation allows people to boat, kayak, walk or fish from dawn to sundown through Labor Day, Sept. 2. In the past, some of those activities have been allowed only by permit.

By the time the L.A. River runs under the bridge at Fletcher, it has coursed and trickled from its source in the Simi Hills before emptying into the Pacific Ocean in Long Beach.

Most of the river was entombed in concrete in the 1930s, a reaction to a series of catastrophic floods. After that, the river became a symbol of Los Angeles' unchecked sprawl, an occasional backdrop for movie car chases — and punch lines.

In the 1980s, environmental groups began pushing to remove the concrete and return the river to its natural state. Since then, voters have approved millions of dollars in bond measures for the development of recreational opportunities along its course.

In 2011, a scenic portion in the San Fernando Valley's Sepulveda Basin opened for guided tours. Tickets sold out in minutes.

Today, hiking and bicycle trails and pocket parks dot its course, and it serves as a habitat for more than 200 species of birds. The opening ceremony for the recreation zone was at Marsh Park, situated on a once-blighted patch of land in the neighborhood between Interstate 5 and the river.

Speaking at the ceremony, City Councilman Ed Reyes said the park and the recreation zone should be a model for the broader reclamation of the river. It's something he's yearned for since he was a child. When he was growing up, Reyes recalled, the parks were riddled with gangs. So he and his friends hung out at the river, even though it was technically off-limits.

"We needed a sanctuary, a place to go, and the river gave us that," Reyes said. "We were told you couldn't go in, so — as 10-year-olds — we went in anyway."

Among the river's champions are Jeff Tipton and Joel Shapiro, two doctors who in 2008 were part of a rogue flotilla that, without permits, kayaked 51 miles of the river over three days to draw attention to the cause. On Monday, they were among the first to try to ply the waterway — legally.

"This is a great start," Tipton said. "But people need to continue to challenge their access to the river."

Schleier's maiden voyage lasted two hours and included a dip when his kayak tipped over in a rough patch. His buddies, film editor Mark Goldberg and hairstylist Trey Burnette, helped him out of the drink, and the trio ventured on. They saw egrets and ducks. And they marveled at how little trash they saw.